calculate the count of object using reduce or filter in javascript

Question

I've written a method to calculate the number of objects in an array which have 'enabled' set to 'true'.

I'm adding 1 to counter each time it finds an object in my array which has 'enabled' set to 'true'.

How could I achieve this without using 'counter' variable and using reduce or filter instead??

Here's my code:

function getCount() {               
    const arr =[[{ "enabled": true }], [{ "enabled": false}, {"enabled": true}]];                       
    var count = 0;
    arr.forEach(function(ar){
        ar.forEach(function(obj){
            if(obj.enabled) {
                count++;
            }
        })
    });
    return count;           
}

yes, that's true, corrected it now! I want to use reduce from ES6. — Sunny
– Sunny, Commented Oct 31, 2018 at 13:10

StudioTime · Accepted Answer · 2018-10-31 17:24:53Z

9

Have a look below, I've added a comment:

[].concat(...arr) /* flatten the array */
.filter(item => item.enabled) /* return only enabled: true */
.length /* get the count */

const arr = [
  [{
    "enabled": true
  }],
  [{
    "enabled": false
  }, {
    "enabled": true
  }]
];
var enabledCount = [].concat(...arr).filter(item => item.enabled).length
console.log(enabledCount)

Or you can use reduce, if you want

const arr = [
  [{
    "enabled": true
  }],
  [{
    "enabled": false
  }, {
    "enabled": true
  }]
];

var enabledCount = arr.reduce(
  (accumulator, currentValue) => accumulator.concat(currentValue), []
).filter(item => item.enabled).length

console.log(enabledCount)

edited Oct 31, 2018 at 17:24

answered Oct 31, 2018 at 13:08

StudioTime

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2 Comments

Sunny Over a year ago

I want to use reduce from ES6

StudioTime Over a year ago

I've added a reduce example

Nicolai Lissau · Accepted Answer · 2021-02-27 19:18:30Z

3

Using a helper reduce function gives the simplest implementation in my opinion:

const arr =[
 [
     {"enabled": true},
     {"enabled": true}
 ],
 [
     {"enabled": false}, 
     {"enabled": true},
     {"enabled": true}
 ]
]; 

// Helper function to count inner arrays
const r = (i) => i.reduce( (p, c) => c.enabled ? p = p + 1 : p, 0)

const count = arr.reduce( (p, c) => p + r(c), 0) // Output: 4

answered Feb 27, 2021 at 19:18

Nicolai Lissau

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1 Comment

Mojtaba Pourmirzaei Over a year ago

if your [arr] has properties ( ike count): THEN arr.reduce((p, c) => (c.prop.enabled ? p + +c.count : p), 0)

Jason Ehmke · Accepted Answer · 2018-10-31 13:08:43Z

1

Would something like this work?

const arr =[[{ "enabled": true }], [{ "enabled": false}, {"enabled": true}]];               
const enabledArray = arr.map(function(item) {
    return item.filter(function(subItem){
        return subItem.enabled === true;
    })
})
const enabledItems = enabledArray.length;

answered Oct 31, 2018 at 13:08

Jason Ehmke

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Comments

Ghighi Eftimie · Accepted Answer · 2018-10-31 13:47:38Z

1

You could do:

const arr = [[{ "enabled": true }], [{ "enabled": false }, { "enabled": true }]];

console.log(
    arr.reduce(
    // Flatten the array of arrays
        (acc, curVal) => acc.concat(curVal), []         
    ).filter(
    // Filter so you have an array with 
    //       objects that have 'enable': true
        (obj) => Object.is(obj['enabled'], true))
    // and then return the length of it
    .length
);

answered Oct 31, 2018 at 13:47

Ghighi Eftimie

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